1. Field of the Invention
The present invention relates to a hydraulic system with an improved complex operation, which can prevent an abrupt operation of a boom of an excavator by delaying the responsibility of a control spool when the boom and an option device (e.g. a hammer, a shear, a rotator, or the like) are simultaneously operated in the excavator.
More particularly, the present invention relates to a hydraulic system with an improved complex operation, which can prevent the generation of shock in a boom by delaying pressure supply during start and end of pilot signal pressure supplied to a spool for controlling an option device when a boom ascending operation and an operation of an option device (e.g. a hammer, a shear, a rotator, or the like) are simultaneously performed or when such a simultaneous operation of the boom and the option device switches over to an independent operation of the boom.
2. Description of the Prior Art
As illustrated in FIG. 1, a hydraulic system with an improved complex operation of the related art includes variable displacement main hydraulic pumps 101 and 101a and a pilot pump 102 operated by an engine; a boom cylinder 118 and an option device (e.g. a hammer or the like) operated by the main hydraulic pumps 101 and 101a; a main control valve (MCV) 104 including a boom spool 106 and an option device spool 119 which are shifted by a pilot signal pressure from the pilot pump 102 to control hydraulic fluid supplied from the main hydraulic pumps 101 and 101a to the boom cylinder 118 and the option device, respectively; an operation (RCV) lever 109 controlling the boom spool 106 of the main control valve 104 by supplying the pilot signal pressure from the pilot pump 102 to the boom spool 106 through an output of an operation signal corresponding to an amount of operation by an operator; an option operation (RCV) pedal 110 controlling the option device spool 119 of the main control valve 104 by supplying the pilot signal pressure from the pilot pump 102 to the option device spool 119 through an output of an operation signal corresponding to the amount of operation by the operator; a confluence spool 107 for controlling the option device, which makes the hydraulic fluid from the main hydraulic pump 101a join the hydraulic fluid on the side of the main hydraulic pump 101 through a confluence flow path a to increase a boom ascending speed when the boom is operated to ascend and which intercepts confluence hydraulic fluid supplied to the boom cylinder 118 and supplies the hydraulic fluid to the option device when a complex work for simultaneously operating the operation lever 109 and the option operation pedal 110 is performed; and a controller 103 outputting an electric control signal to a proportional control valve 105 for the option device through a signal cable 115 so that the confluence spool 107 for controlling the option device is shifted by pilot signal pressure (i.e. second signal pressure) that passes through the proportional control valve 105 for the option device to intercept the confluence hydraulic fluid supplied to the boom cylinder 118 through the confluence flow path a and to supply the hydraulic fluid to the option device, when a complex operation for simultaneously operating the boom cylinder 118 and the option device is performed.
In the drawing, the unexplained reference numerals 122 and 123 denote regulators that variably control the discharged flow rate of the main hydraulic pumps 101 and 101a by controlling the inclination angles of the swash plates of the main hydraulic pumps 101 and 101a in proportion to the control signal (i.e. the second signal pressure) input from the controller 103 to electronic proportional valves 120 and 121.
The above-described confluence spool 107 for controlling the option device has a confluence function. That is, since a boom confluence function is required only to make the boom ascend, the confluence spool 107 for the option device has the boom confluence function in one direction and has an option device operation function or a flow control function for the option device (corresponding to an option flow control spool) in the other direction.
Accordingly, if an operator operates the operation lever 109 to make the boom ascend, the pilot signal pressure discharged from the pilot pump 102 is supplied to the boom spool 106 through the operation lever 109 and a flow path 111a in order to shift the boom spool. Accordingly, the hydraulic fluid discharged from the main hydraulic pump 101 is supplied to the boom cylinder 118 via the boom spool 106.
At the same time, as the confluence spool 107 is shifted by the pilot signal pressure supplied from the pilot pump 102 through the flow path 111b, the hydraulic fluid discharged from the main hydraulic pump 101a joins the hydraulic fluid on the side of the main hydraulic pump 101 through the confluence spool 107 and the confluence flow path a in order, and the confluence hydraulic fluid is supplied to the boom cylinder 118.
Accordingly, the boom ascending speed can be increased by the hydraulic fluid simultaneously supplied from the main hydraulic pumps 101 and 101a to the boom cylinder 118.
As described above, if the option device (e.g. a hammer or the like) is operated by the option operation pedal 110 during the ascending of the boom, the controller 103 senses the pilot signal pressure for operating the option device that is supplied from the pilot pump 102 to the flow path 112, and outputs the electric control signal to the proportional control valve 105 for the option device.
Accordingly, the pilot signal pressure in a flow path 114, having passed through the proportional control valve 105, operates the flow control spool side for the option device of the confluence spool 107, and thus the hydraulic fluid from the main hydraulic pump 101a is supplied to the option device through the option device spool that is shifted by the pilot signal pressure (see the graph of the pilot signal pressure control diagram of FIG. 2) in the flow path 112.
In this case, the boom confluence hydraulic fluid, which is supplied to the boom cylinder 118 to make the boom ascend, is intercepted. That is, by supplying the hydraulic fluid from one of the main hydraulic pumps 101 and 101a to the boom cylinder 118 and the option device, respectively, the boom cylinder 118 and the option device can be simultaneously operated.
In the hydraulic system of the related art, if the option device is operated during the ascending of the boom or the option device is stopped during the ascending of the boom, the boom confluence function and the option device flow control function are simultaneously performed by one confluence spool 107. Accordingly, the pilot signal pressure is instantaneously applied in an opposite direction (indicated as t1 and t2 in the graph of FIG. 2) to operate the confluence spool 107 for controlling the option device, and thus the boom ascending speed is abruptly changed to generate shock.
That is, in the case where the boom is first operated to ascend and then the option device is operated, as shown as the pilot signal pressure control curve illustrated in FIG. 2, the boom confluence operation is instantaneously interrupted, and thus the boom ascending speed is abruptly lowered to cause the shock generation.
In contrast, even in the case where the option device is first stopped during the simultaneous operation of the boom and the option device, the boom confluence operation is instantaneously performed, and thus the boom ascending speed is abruptly increased to generate the shock, resulting in the clattering of the equipment.